def slidewindow(s):
    window = {}
    needs = {}
    left = 0
    right = 0
    valid = 0

    while right < len(s):
        c = s[right]
        if c in window:
            window[c] += 1
        else:
            window[c] = 1
        

        right += 1

        while left < right and  window needs shrink:
            d = s[left]
            if d in needs:
                window[d] -= 1
                valid -= 1
            left += 1
        
